SAN FRANCISCO  A federal judge has ordered officials to study whether 66 common agricultural pesticides are harming a red-legged frog believed to have inspired a short story by Mark Twain.

U.S. District Judge Jeffrey White ruled Monday that the Environmental Protection Agency must consult with biologists to determine whether, as environmentalists allege, the pesticides are harming the frog.

The California red-legged frog was listed as a threatened species in 1996 and has lost about 70 percent of its numbers. It gained fame in Twain's tale "The Celebrated Jumping Frog of Calaveras County."

The EPA said in a statement it disagreed with the decision and was reviewing its options. White ordered the government and the Center for Biological Diversity, which brought the suit, to agree to a time when the studies should be complete.

The California red-legged frog is the largest frog native to the western United States. Females are larger than males, about 5 1/2 inches versus 4 1/2 inches. The adults usually have red legs.